Corrosion inhibiting, freezing point lowering compositions

ABSTRACT

The present invention relates to corrosion inhibiting, freeze point lowering compositions comprising a mixture of a freeze point lowering agent and a corrosion inhibiting compound. The corrosion inhibiting, freeze point lowering compositions can be used in deicing brines or deicing solutions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. patent application Ser. No. 14/089,054,filed on Nov. 25, 2013, which claims priority to U.S. Provisional PatentApplication No. 61/730,673, filed on Nov. 28, 2012, the contents ofwhich are fully incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to corrosion inhibiting composition with improvedstability under cold storage conditions. The compositions comprise amixture of a freeze point lowering agent and a corrosion inhibitingcompound. The freeze point lowering agent used in the composition of thepresent invention is potassium chloride, ammonium chloride, lithiumchloride, potassium acetate, ammonium acetate, lithium acetate,potassium nitrate, ammonium nitrate or lithium nitrate and the corrosioninhibiting compound is a hydroxycarboxylic acid salt, namely, sodiumgluconate. The corrosion inhibiting, freeze point lowering compositionscan be used in deicing brines or deicing solutions.

BACKGROUND OF THE INVENTION

Freezing point lowering agents are in widespread use for a variety ofpurposes, especially to reduce the freezing point of an aqueous systemso that ice cannot be formed or to melt formed ice. Generally, freezingpoint lowering agents depend for their effectiveness upon the molarfreezing point lowering effect, the number of species which are madeavailable and the degree to which the agent can be dispersed in theliquid phase in which the formation of ice is to be precluded and/or iceis to be melted.

A common use for freeze point lowering agents is in road deicers.Traditionally, deicers comprising a solid salt, such as sodium chloriderock salt, were spread onto roadways (solid deicers); however, there isa growing trend to use liquid deicers for improved deicer performance.In fact, aqueous solutions of salts (liquid deicers) are more effectiveat preventing ice formation than solid salt because the solution can beapplied more evenly on the road and is not displaced by vehicle traffic,thus resulting in a more efficient use of the salt.

The most pervasive of the commonly used products for deicing are commonsalt, calcium chloride, magnesium chloride, acetates and urea, withcommon salt (sodium chloride) being the least expensive and mostcommonly used. Common salt is widely used to melt ice on road surfacesand the like. In this manner, the salt forms a solution with theavailable liquid in contact with the ice and thereby forms a solutionwith a lower freezing point than the ice itself so that the ice ismelted. Chloride salts, while inexpensive, suffer from relatively severedrawbacks, such as the harmful effects on surrounding vegetation bypreventing water absorption in the root systems, and its corrosiveeffects on roadway infrastructure and motor vehicles. A downside to theuse of liquid salt deicers is increased corrosion problems arising fromthe use of salt water. To mitigate the corrosive effects corrosioninhibitors are added to the salt solution (See, for example, U.S. Pat.No. 7,658,861).

Typically, liquid deicers comprise two components which originate fromtwo different sources, namely, (1) a brine; and (2) a corrosioninhibitor containing solution (which is typically supplied in the formof a concentrated solution). The brine and corrosion inhibitorcontaining solution are stored separately until combined in the fieldwhen needed at the time of use. One of the key requirements forcorrosion inhibiting containing solutions is that these solutions bestable in cold storage. Specifically, the corrosion inhibitingcontaining solution cannot freeze above a certain temperature or formany insoluble material. Therefore, freeze point lowering agents must beadded to the corrosion inhibitor solutions to mitigate ice formation.Commonly the freeze point agents are the same salts that constitute thedeicing solution, namely sodium chloride or magnesium chloride. However,the addition of freeze point lowering agents to the corrosion inhibitorsolutions causes problems. Specifically, these agents tend to forminsoluble salts with the corrosion inhibitor or promote crystallizationof the corrosion inhibitor through the common ion effect. Therefore,there is a need in the art for new corrosion inhibiting, freeze pointlowering agents that when stored in cold temperatures, sufficientlylower the freeze point while forming minimal to no solids.

SUMMARY OF THE INVENTION

In one aspect, the present invention relates to a corrosion inhibitingcomposition that is stable to cold storage temperatures below about 15°F. The composition comprises: a mixture of water, a freeze pointlowering agent and a corrosion inhibiting compound, wherein the freezepoint lowering agent is potassium chloride, ammonium chloride, lithiumchloride, potassium acetate, ammonium acetate, lithium acetate,potassium nitrate, ammonium nitrate, lithium nitrate or mixtures thereofand the corrosion inhibiting compound is sodium gluconate, wherein saidcomposition is stable to cold storage temperatures at or below about 15°F.

The above described corrosion inhibiting, freeze point lowering cancomprise about 25% by weight to about 40% by weight of the corrosioninhibiting compound. Additionally, the above described corrosioninhibiting, freeze point lowering composition can comprise about 1% byweight to about 50% by weight of a freeze point lowering agent.

In another aspect, the present invention relates to a liquid compositioncomprising an aqueous solution of a freeze point depressant and theabove described corrosion inhibiting freeze point lowering composition.In the liquid composition, the aqueous solution can be water. In theliquid composition, the freeze point depressant is selected from thegroup consisting of sodium chloride, magnesium chloride, calciumchloride, potassium chloride, calcium magnesium acetate, potassiumacetate, urea, and ammonium sulfate. In the liquid composition, thecomposition can comprise about 15% by weight to about 35% by weight of afreeze point depressant.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows solutions of 34% sodium gluconate and freeze pointdepressing salts (NaCl, KCl, MgCl₂ or NH₄Cl) that were prepared on aweight/weight basis as described in Example 1. Specifically, thisphotograph shows the results when the solutions were placed in a freezerset at a temperature of 15° F. for 3 days. Specifically, the resultingsolutions: A) were frozen; B) exhibited crystal formation as seen withsodium gluconate mixed with NaCl; C) exhibited a thick white precipitateformed by combination of sodium gluconate and MgCl₂ or CaCl₂; or D) asolid free solution as seen by combining sodium gluconate and KCl orNH₄Cl.

DETAILED DESCRIPTION OF THE INVENTION

The invention describes novel corrosion inhibiting, freeze (or freezing)point lowering compositions suitable for use in a deicing composition.The corrosion inhibiting, freeze point lowering compositions describedherein comprise a mixture of a freeze point lowering agent and acorrosion inhibiting compound. The corrosion inhibiting, freeze pointlowering compositions of the present invention are stable to coldstorage temperatures at and below about 15° F. (namely, about 15° F.,about 14° F., about 13° F., about 12° F., about 11° F., about 10° F.,about 9° F., about 8° F., about 7° F., about 6° F., about 5° F., about4° F., about 3° F., about 2° F., about 1° F., about 0° F.). In anotheraspect, the corrosion inhibiting, freeze point lowering compositions ofthe present invention are stable to cold storage temperatures of fromabout 0° F. to about 15° F., from about 1° F. to about 15° F., fromabout 2° F. to about 15 ° F., from about 3° F. to about 15° F., fromabout 4° F. to about 15° F., from about 5° F. to about 15° F., fromabout 6° F. to about 15° F., from about 7° F. to about 15° F., fromabout 8° F. to about 15° F., from about 9° F. to about 15° F. or fromabout 10° F. to about 15° F. As used herein the term “stable” means thatthe corrosion inhibiting, freeze point composition of the presentinvention, when stored at a temperature at or below about 15° F.(namely, about 15° F., about 14° F., about 13° F., about 12° F., about11° F., about 10° F., about 9° F., about 8° F., about 7° F., about 6°F., about 5° F., about 4° F., about 3° F., about 2° F., about 1° F.,about 0° F.), are (1) not frozen or do not contain any ice or do notcontain any ice crystals; and (2) are substantially free of any solids(meaning that the composition contains less than 5% solids).

The freeze point lowering agent comprises potassium chloride, ammoniumchloride, lithium chloride, potassium acetate, ammonium acetate, lithiumacetate, potassium nitrate, ammonium nitrate, lithium nitrate ormixtures thereof. The corrosion inhibiting compound is ahydroxycarboxylic acid salt, namely, sodium gluconate.

The freezing point lowering agent can be used in any form (namely,amorphous or crystalline) in the corrosion inhibiting, freeze pointlowering composition.

The corrosion inhibitor can be used in any form (namely, amorphous orcrystalline) in the corrosion inhibiting, freeze point loweringcomposition.

The amount of freeze point lowering agent contained in the corrosioninhibiting, freeze point lowering composition is from about 1% by weightto about 50% by weight. In one aspect, the corrosion inhibiting, freezepoint lowering composition contains from about 1% to about 45% by weightof a freeze point lowering agent, from about 1% to about 40% by weightof a freeze point lowering agent, from about 1% to about 35% by weightof a freeze point lowering agent, from about 1% to about 30% by weightof a freeze point lowering agent, from about 1% to about 25% by weightof a freeze point lowering agent, from about 1% to about 20% by weightof a freeze point lowering agent, from about 1% to about 15% by weightof a freeze point lowering agent, from about 1% to about 10% by weightof a freeze point lowering agent or from about 1% to about 5% by weightof a freeze point lowering agent. Specifically, the composition cancomprise at least 1% by weight of a freeze point lowering agent, atleast 2% by weight of a freeze point lower agent, at least 3% by weightof a freeze point lowering agent, at least 4% by weight of a freezepoint lowering agent, at least 5% by weight of a freeze point loweringagent, at least 6% by weight of a freeze point lowering agent, at least7% by weight of a freeze point lowering agent, at least 8% by weight ofa freeze point lowering agent, at least 9% by weight of a freeze pointlowering agent, at least 10% by weight of a freeze point lowering agent,at least 11% by weight of a freeze point lowering agent, at least 12% byweight of a freeze point lowering agent, at least 13% by weight of afreeze point lowering agent, at least 14% by weight of a freeze pointlowering agent, at least 15% by weight of a freeze point lowering agent,at least 16% by weight of a freeze point lowering agent, at least 17% byweight of a freeze point lowering agent, at least 18% by weight of afreeze point lowering agent, at least 19% by weight of a freeze pointlowering agent, at least 20% by weight of a freeze point lowering agent,at least 21% by weight of a freeze point lowering agent, at least 22% byweight of a freeze point lowering agent, at least 23% by weight of afreeze point lowering agent, at least 24% by weight of a freeze pointlowering agent, at least 25% by weight of a freeze point lowering agent,at least 26% by weight of a freeze point lowering agent, at least 27% byweight of a freeze point lowering agent, at least 28% by weight of afreeze point lowering agent, at least 29% by weight of a freeze pointlowering agent, at least 30% by weight of a freeze point lowering agent,at least 31% by weight of a freeze point lowering agent, at least 32% byweight of a freeze point lowering agent, at least 33% by weight of afreeze point lowering agent, at least 34% by weight of a freeze pointlowering agent, at least 35% by weight of a freeze point lowering agent,at least 36% by weight of a freeze point lowering agent, at least 37% byweight of a freeze point lowering agent, at least 38% by weight of afreeze point lowering agent, at least 39% by weight of a freeze pointlowering agent, at least 40% by weight of a freeze point lowering agent,at least 41% by weight of a freeze point lowering agent, at least 42% byweight of a freeze point lowering agent, at least 43% by weight of afreeze point lowering agent, at least 44% by weight of a freeze pointlowering agent, at least 45% by weight of a freeze point lowering agent,at least 46% by weight of a freeze point lowering agent, at least 47% byweight of a freeze point lowering agent, at least 48% by weight of afreeze point lowering agent, at least 49% by weight of a freeze pointlowering agent or at least 50% by weight of a freeze point loweringagent.

The amount of the corrosion inhibitor contained in the corrosioninhibiting, freeze point lowering composition is from about 25% byweight to about 40% by weight. In another aspect, the corrosioninhibiting, freeze point lowering composition contains from about 25% toabout 35% by weight of a corrosion inhibitor or from about 25% to about30% by weight of a corrosion inhibitor. Specifically, the compositioncan comprise at least 25% by weight of a corrosion inhibitor, at least26% by weight of a corrosion inhibitor, at least 27% by weight of acorrosion inhibitor, at least 28% by weight of a corrosion inhibitor, atleast 29% by weight of a corrosion inhibitor, at least 30% by weight ofa corrosion inhibitor, at least 31% by weight of a corrosion inhibitor,at least 32% by weight of a corrosion inhibitor, at least 33% by weightof a corrosion inhibitor, at least 34% by weight of a corrosioninhibitor, at least 35% by weight of a corrosion inhibitor, at least 36%by weight of a corrosion inhibitor, at least 37% by weight of acorrosion inhibitor, at least 38% by weight of a corrosion inhibitor, atleast 39% by weight of a corrosion inhibitor at least 40% by weight of acorrosion inhibitor.

The corrosion inhibiting, freeze point lowering composition can alsocontain anti-caking agents, flow enhancers, thickeners, colorants andthe like.

The present invention also relates to an aqueous composition (such aswater) containing a combination of a brine and the corrosion inhibiting,freeze point lowering composition described herein and methods formaking such a composition. Such a composition can be prepared by mixingor dissolving a brine containing the freeze point depressant and thecorrosion inhibiting, freeze point lowering composition of the presentinvention in water or another suitable liquid to form the liquidcomposition using routine techniques known in the art. The freeze pointdepressant used in the brine is selected from the group consisting ofsodium chloride, magnesium chloride, calcium chloride, potassiumchloride, calcium magnesium acetate, potassium acetate, urea ammoniumsulfate and mixtures thereof.

The present invention also relates to a method of deicing. The methodinvolves the step of applying an aqueous composition comprising a brinecontaining a freeze point depressant and the corrosion inhibiting,freeze point lowering composition of the present invention to a surfaceor area of interest (such as a road, bridge, walkway, highway, etc.).

The corrosion inhibiting, freeze point lowering composition of thepresent invention exhibits improved properties over corrosioninhibiting, freeze point lowering mixtures comprising (1) sodiumgluconate; and (2) sodium chloride, magnesium chloride, calcium chlorideor mixtures thereof. Specifically, corrosion inhibiting, freeze pointlowering compositions of the present invention (i) sufficiently lowerthe freeze point; and (ii) do not form solids, particularly whencompared to corrosion inhibiting, freeze point lowering compositionscomprising (1) sodium gluconate and (2) sodium chloride, magnesiumchloride, calcium chloride or mixtures thereof.

It will be apparent to those of skill in the art that variations may beapplied to the compositions and methods described herein and in thesteps or in the sequence of steps of the method described herein withoutdeparting from the concept, spirit and scope of the invention. Morespecifically, it will be apparent that certain agents which are bothchemically and physiologically related may be substituted for the agentsdescribed herein while the same or similar results would be achieved.All such similar substitutes and modifications apparent to those skilledin the art are deemed to be within the spirit, scope and concept of theinvention.

It is to be understood that the invention is not limited in itsapplication to the details of construction and the arrangement ofcomponents set forth in the following description. Also, it is to beunderstood that the phraseology and terminology used herein is for thepurpose of description and should not be regarded as limiting. The useof “including,” “comprising,” or “having” and variations thereof hereinis meant to encompass the items listed thereafter and equivalentsthereof as well as additional items.

It also is understood that any numerical range recited herein includesall values from the lower value to the upper value. For example, if aconcentration range is stated as 1% to 50%, it is intended that valuessuch as 2% to 40%, 10% to 30%, or 1% to 3%, etc., are expresslyenumerated in this specification. These are only examples of what isspecifically intended, and all possible combinations of numerical valuesbetween and including the lowest value and the highest value enumeratedare to be considered to be expressly stated in this application.

The following non-limiting examples are purely illustrative.

Example 1

Solutions of sodium gluconate and freeze point depressing salts wereprepared on a weight to weight basis as shown below in Table 1. Eachsolution comprises a fixed 34% (w/w) sodium gluconate and a range of afreeze point depressing salt (Table 1). The solutions were placed in afreezer a temperature set to 15° F. for 3 days. Ice and insoluble solidformation was noted when present. FIG. 1 visually depicts representativeexamples of the results.

TABLE 1 Solutions of 34% sodium gluconate and freeze point depressingsalts at various concentrations were prepared on a weight/weight basisas described below. Freeze point Representative depressant (% w/w) 3days, 15° F. photo NaCl 2% Frozen A 5% Crystalization B 10% Crystalization B KCl 2% No ice, no crystals D 5% No ice, no crystals D10%  No ice, no crystals D NH₄Cl 2% No ice, no crystals D 5% No ice, nocrystals D 10%  No ice, no crystals D MgCl₂ 2% Heavy white precipitationC 5% Heavy white precipitation C 10%  Heavy white precipitation C CaCl₂2% Heavy white precipitation C 5% Heavy white precipitation C 10%  Heavywhite precipitation C

As shown in the above Table 1 and in FIG. 1, mixtures of sodiumgluconate and NaCl resulted in crystal formation. Mixtures of sodiumgluconate and MgCl₂ or CaCl₂ resulted in a thick chalky precipitation.Mixtures of sodium gluconate and KCl or NH₄Cl resulted in no solidformation.

What is claimed is:
 1. A corrosion inhibiting composition stable to coldstorage temperatures below about 15° F., the composition comprising: amixture of water, a freeze point lowering agent and a corrosioninhibiting compound, wherein the freeze point lowering agent ispotassium chloride, ammonium chloride, lithium chloride, potassiumacetate, ammonium acetate, lithium acetate, potassium nitrate, ammoniumnitrate, lithium nitrate or mixtures thereof and the corrosioninhibiting compound is sodium gluconate, wherein said composition isstable to cold storage temperatures at or below about 15° F.
 2. Thecorrosion inhibiting, freeze point lowering composition of claim 1,wherein the composition comprises about 25% by weight to about 40% byweight of the corrosion inhibiting compound.
 3. The corrosioninhibiting, freeze point lowering composition of claim 1, wherein thecomposition comprises about 1% by weight to about 50% by weight of afreeze point lowering agent.
 4. A liquid composition comprising anaqueous solution of a freeze point depressant and the corrosioninhibiting freeze point lowering composition of claim
 1. 5. The liquidcomposition of claim 4, wherein the aqueous solution is water.
 6. Theliquid composition of claim 4, wherein the freeze point depressant isselected from the group consisting of sodium chloride, magnesiumchloride, calcium chloride, potassium chloride, calcium magnesiumacetate, potassium acetate, urea, and ammonium sulfate.
 7. The liquidcomposition of claim 6, wherein the composition comprises about 15% byweight to about 35% by weight of a freeze point depressant.